feat(docs): add information for testing PRs

docs/docs/customization.md

@@ -3,6 +3,9 @@ title: Customizing ZMK/`zmk-config` folders
 sidebar_label: Customizing ZMK
 ---
 
+import Tabs from '@theme/Tabs';
+import TabItem from '@theme/TabItem';
+
 After verifying you can successfully flash the default firmware, you will probably want to begin customizing your keymap and other keyboard options.
 [In the initial setup tutorial](user-setup), you created a Github repository called `zmk-config`. This repository is a discrete filesystem which works
 with the main `zmk` firmware repository to build your desired firmware. The main advantage of a discrete configuration folder is ensuring that the
@@ -28,6 +31,75 @@ various config settings that can be commented/uncommented to modify how your fir
 Once you have the basic user config completed, you can find the keymap file in `config/<shield>.keymap` and customize from there.
 Refer to the [Keymap](/docs/features/keymaps) documentation to learn more.
 
+## Testing features
+
+Testing features will require you to modify the `west.yml` file. You will need to add a new remote for the pull request you would like to test,
+and change the selected remote and revision for the `zmk` project.
+
+<Tabs
+defaultValue="zmk"
+values={[
+{label: 'Default', value: 'zmk'},
+{label: 'PR685: Macros', value: 'macros'},
+{label: 'PR649: Add &sleep behavior', value: 'sleep'},
+]}>
+<TabItem value="zmk">
+
+```
+manifest:
+  remotes:
+    - name: zmkfirmware
+      url-base: https://github.com/zmkfirmware
+  projects:
+    - name: zmk
+      remote: zmkfirmware
+      revision: main
+      import: app/west.yml
+  self:
+    path: config
+```
+
+</TabItem>
+<TabItem value="macros">
+
+```
+manifest:
+  remotes:
+    - name: zmkfirmware
+      url-base: https://github.com/zmkfirmware
+    - name: okke-formsma
+      url-base: https://github.com/okke-formsma
+  projects:
+    - name: zmk
+      remote: okke-formsma
+      revision: macros
+      import: app/west.yml
+  self:
+    path: config
+```
+
+</TabItem>
+<TabItem value="sleep">
+
+```
+manifest:
+  remotes:
+    - name: zmkfirmware
+      url-base: https://github.com/zmkfirmware
+    - name: mcrosson
+      url-base: https://github.com/mcrosson
+  projects:
+    - name: zmk
+      remote: mcrosson
+      revision: feat-behavior-sleep
+      import: app/west.yml
+  self:
+    path: config
+```
+
+</TabItem>
+</Tabs>
+
 ## Publishing
 
 After making any changes you want, you should commit the changes and then push them to GitHub. That will trigger a new